1. Field of the Present Invention
The present invention relates to a moisture detector for detecting moisture percentage in a detection target that may contain moisture, for example, garbage or soil, and further, to a moisture detector to be used for detecting the start of a rainfall so as to prevent unnecessary watering during the rainfall or protect laundry, agricultural harvest, etc. against rain to maintain their dry condition.
2. Description of a Related Art
As a method of disposal of garbage, there is a method of decomposition disposal utilizing aerobic bacteria for fermentation of the garbage. In such disposal method, for easy activation of the aerobic bacteria, ideas are required for controlling the temperature, the amount of oxygen, moisture and so on in the garbage in accordance with the properties of the aerobic bacteria.
Japanese Patent Application Publication JP-A-2000-288514 discloses a garbage disposer for disposing of garbage by utilizing bacteria. In this garbage disposer, garbage is charged from the garbage charge opening, agitation blades are rotated by a motor, and the garbage is agitated by the agitation blades. Here, for easy activation of the aerobic bacteria, the garbage is heated by a heater. The heat temperature is detected by a temperature sensor so as to be proper heat temperature. However, the garbage disposer include no moisture detector for detecting the moisture percentage in the garbage, and therefore, the garbage disposal under the environment in which moisture exists to such an extent that bacteria are easily activated is not considered.
The environment in which the aerobic bacteria activate and proliferate best is an environment in which the moisture percentage is, for example, 60%. If the moisture percentage is less or more than that, there arise not only the problem of taking long time for the composition disposal of garbage, but also a problem of giving out an abnormal odor or the like. Furthermore, when the garbage is too much dried, there arises a problem that the fine powder of the bacteria bed flies, and thereby, clogging occurs in the piping line or deodorizing line.
By the way, since the garbage discharged from cooking places contains considerable moisture, when new garbage is charged into the garbage disposer, the moisture percentage within the garbage disposer rises to nearly 100%. Afterwards, the moisture percentage within the garbage disposer is gradually reduced and, after the condition in which the moisture percentage becomes optimum lasts in a relatively short period, led to the dry condition. Since such cycle is repeated in the conventional garbage disposer, it can be hardly say that the condition in which the aerobic bacteria are activated easily is created stably.
Generally, as a method of detecting moisture percentage or humidity, there are an electric resistance method, a heat capacity method, an electric capacity method, an optical method, etc., each of which has advantages and disadvantages. As a representative one of those, the electric resistance method suitable for detecting humidity in the air can be cited. When a detector is used in a relatively clear atmosphere as in the weather observation, an open case type detector according to the electric resistance method, that is not enclosed in a closed case, may be sufficient.
However, in order to detect the moisture percentage in the dirt such as garbage, the open case type detector is inappropriate, but a closed case type detector that is enclosed within the closed case is appropriate.
Further, in the case of trying to detect the raindrop hits as in a rainfall detector, the open case type detector is also inappropriate. The reason is as follows. When the raindrops drop on the dirt and dust which have been accumulated on the detector due to a spell of fine weather, the function as a sensor for indicating the sensing results on the basis of changes in the resistance value for moment to moment is lost because the dirt and dust stick to the sensor, and therefore, cleaning is required. Thus, for the rainfall detector, the closed case type detector is also appropriate.
Generally, if the moisture percentage is low in the detection target as in the case of detecting the moisture percentage in the air, the open case type detector can be used, however, if the moisture percentage is high in the detection target, the closed case type detector is appropriate. Accordingly, how to realize a closed case type moisture detector according to the heat capacity method and having a relatively simple constitution becomes a problem.